In order to understand how MO drives work, magneto-optical offers a self-descriptive starting point. Data are written magnetically, unlike CD and DVD drives. Unlike a hard drive, however, the media need not be kept in a clean environment, i.e. practically vacuum-packed. The plastic envelope of MO media is thus only there to protect the surface.
The real highlight, however, is the composition of the surface, because it can only be magnetized or demagnetized after it has been heated to certain temperatures. This occurs optically, with the use of a laser.
In order for it to work perfectly, the timing of the two components has to be just right. Accordingly, that leads to two results that are typical of MOs: One, the stored data are preserved more securely than on a hard drive, and two, the MO drives are, precisely because of this laborious process, considerably slower to write to than hard drives or CD/DVD drives.
Very High Data Security
Because the magnetic capacity of the MO media is restricted to a narrow temperature range, magnets cannot accidentally or maliciously destroy the data - as can occur with hard drives. Even if the media were heated, data loss would be unlikely - unless the temperature were so high that the materials were destroyed, as in a house fire. But then you would primarily have other problems.
Enclosing the storage media in a plastic case would protect it for the most part against mechanical damage. The principle is simple and similar to conventional 3.5" floppies.
The media can survive a fall from "normal" altitudes, e.g. from a desk to a hard floor, without problem. That would be the end of a hard drive.
Even the long-term safety of your data is guaranteed on MO media, according to Fujitsu. However, we will assume that, for storage times of more than 5-10 years, you will look for another medium in time, as replacement parts, media and computer interfaces (USB, FireWire) will all most likely be replaced with considerably more powerful alternatives.
From this standpoint, the CD or DVD, handled correctly, is still the biggest competition for magneto-optical solutions, because if their surfaces are not exposed to harmful gases or sunlight, and are treated carefully, (i.e. not scratched), high-quality media should easily last 10 years. If you want to play it safe, you will have several copies of each media stored in different places.
However, the more often the storage media are accessed, the more of an edge the MO drive has. According to Fujitsu the media actually can be written to millions of times, while CD-RWs or DVD±RWs only assume 1,000 write processes.
A further security feature may not occur to you at first, because most users would see it as a disadvantage: the media can, of course, only be read on corresponding drives. In other words, if an MO diskette containing critical data should fall into the wrong hands, the finder would first have to obtain an MO drive.
Purpose: Regular Use
You might now be asking why it absolutely has to be an MO drive. Shouldn't write protection be just as possible with CD/DVD burners? Yes and no. In principle, it is feasible, but only if both the drive and the operating system support the Mount Rainier standard. Present software solutions cannot be called secure in this context. For the customer, the only thing that matters is the maximum data security achievable by reasonable means, and CD or DVD do not provide that.
Add to this another factor, which applies above all to governmental bodies and several other professional groups: they must be able to provide multiple revisions. Typical customers for MO solutions are doctors and clinics, or engineering firms.